The embodiments described herein relate generally to an electric machine, and more specifically, to an electric machine which includes a component made by a process where magnetically and non-magnetically conductive layers are successively applied to form the component.
An electric machine is typically in the form of an electric generator or an electric motor. Electric machines may be radial flux machines where the flux is generally radial and axial flux machine where the flux is generally axial or a mix of radial and axial flux. As a vast majority of electric machines are radial flux the discussion herein is generally for a radial flux machine. It should be appreciated that axial flux machines and machines that are a mix of radial and axial flux share many of the performance issues of radial flux machines. The machine typically has a centrally located shaft that rotates relative to the machine. Electrical energy applied to coils within the motor initiates this relative motion which transfers the power to the shaft and, alternatively, mechanical energy from the relative motion of the generator excites electrical energy into the coils. For expediency the machine will be described hereinafter as a motor. It should be appreciated that a motor may operate as a generator and vice versa.
A stationary assembly, also referred to as a stator, includes a stator core and coils or windings positioned around portions of the stator core. It is these coils to which energy is applied to initiate this relative motion which transfers the power to the shaft. These coils are formed by winding wire, typically copper, aluminum or a combination thereof, about a central core to form the winding or coil. An electric current is directed through the coils which induces a magnetic field. It is the magnetic field that initiates this relative motion which transfers the power to the shaft.
In an assembled configuration, the coils are positioned in a spaced apart relationship about the stationary assembly that typically has a generally hollow cylindrical configuration with the coils positioned internally. The power of the electric motor is dependent on the amount of energy that may be applied to the coils and that amount of energy is proportional to the amount of wire that may be positioned about the stationary assembly. The amount of wire positioned about the stationary assembly is typically referred to as the slot fill. Placing as much wire in the coils as possible, also known as maximizing the slot fill is thus desirable.
Typically the stator core is made of a magnetically conductive material, typically a ferrous material to assist in strengthening and directing the magnetic field induced by the coils. When the current passes through the coils to induce the magnetic field, eddy currents are generated in the stator core. These eddy currents result in lower machine efficiencies. These currents flow generally in a direction parallel to the shaft of the machine in a radial flux machine. Note that these currents flow generally in a direction perpendicular to the shaft of the machine in an axial flux machine.
To reduce these eddy current losses, rather than have a solid stator core, the stator core typically is designed with a series of parallel plates, typically called laminations, typically stamped from sheet steel. The laminations extend perpendicularly to the shaft. The core is typically produced by stacking a plurality of rigid hollow laminations and joining them to form the rigid hollow cylindrical core. The core is typically produced by stacking a plurality of rigid hollow laminations and joining them to form the rigid hollow cylindrical core.
Typically, the rigid hollow cylindrical core is formed with internal protrusions of teeth around which the coils are wound. One winding method requires the wire to be fed around the teeth with a device called a needle. The need to provide for movement of the needle around the teeth limits the amount of wire that may be used to form the coil. This method is slow and either requires substantial equipment investment and/or substantial labor costs.
Grains in the steel used to make such laminations may be oriented in a desired direction to assist in improving the magnetic field, and the efficiency of the electric machine. Such orientation is limited to a linear direction. While such orienting is helpful, it is suboptimal, because the desired magnetic field direction is a very complex shape.
Transformers and certain sections of electric machines use sheet-steel material or laminations that has highly favorable directions of magnetization along which the core loss is low and the permeability is high. Grains in the steel used to make such laminations may be oriented in a desired direction to assist in improving the magnetic field, and the efficiency of the electric machine. The material with such aligned or oriented grains is termed grain-oriented steel. The reason for this property lies in the atomic structure of the simple crystal of the silicon-iron alloy, which is a body centered cube; each cube has an atom at each corner as well as one in the center of the cube. In the cube, the easiest axis of magnetization is the cube edge, the diagonal across the cube face is more difficult, and the diagonal through the cube is the most difficult. By suitable manufacturing technique, the majority of the cube edges are aligned in the rolling direction to make it a favorable direction of magnetization. The behavior in this direction is superior in core loss and required magnetization to nonoriented steels, so that the oriented steels can be operated at higher flux densities than the nonoriented grades.
The present invention is directed to alleviate at least some of these problems with the prior art.